the base material, if this case clay, is the same, the ADa stuff has other things added. Power sand is a porous volcanic substratnce with a general fert added. The method caps this with the clay. This keeps the NH4 down there till bacteria convert it to NO3.

Soil and sand methods do the same thing.
Soil is more reductive and maintains the NH4 longer(too reductive for the bacteria to NH4=> NO3). Those bacteria need O2.

That works in the upper layers in diffusion is relatively slow, but any substrate fert last only a few weeks, except traces..........

I can dose KNO3/KH2PO4 right away also to the water column and get the same result.

Regards,
Tom Barr